40ggarlic cloves(1.4 ounces), peeled, washed and thinly sliced
40gginger(1.4 ounces), peeled, washed, and thinly sliced
70ggreen onion(2.4 ounces), peeled, washed, and thinly sliced
1.5cupscooking oil(I used rice bran oil, but canola or grape-seed oil can work too.)
Add the Korean chili flakes in a medium sized heat proof bowl or a small stainless steel pot. (A pot with a long handle is a great option as you can filter the oil easier later on.)
Add in the garlic, ginger, green onion into a wide base saucepan or sauté pan. Pour the cooking oil and bring it to boil over medium high heat until the aromatics start turning light brown or until the oil temperature reaches about 170 C / 340 F when you use an instant thermometer. Depending on your stove type, it will be between 5 to 10 mins to reach this point. Another sign you could use is by splashing a small amount (about 2 tsp) of boiled oil over the Korean chili flakes. If the temperature is high enough, the chili flakes will make some sizzling bubbles. Turn the heat off.
Scoop out the aromatic vegetables using a slotted spoon or tongs and discard. Or strain them while pouring the oil over the chili flakes (from step 1) in a few batches. It will make small sizzling bubbles initially then die down as it cools. Stir around the chili flakes and oil to mix them well. Steep the chili flakes for 15 mins and allow it to bring out the flavor and color.
Filter the oil using a funnel and filter paper and transfer the chili oil into a sterilized glass jar. (Most Koreans do not keep the residual chili flakes after steeping but if you want to you can keep them. Just skip the filtering process.) To store, refrigerate the jar. Try to use the oil within 2 months. To use, give the oil a stir before using and always use a clean spoon to scoop it out.
If you want hotter Korean chili oil, you may mix in some dried red chilies and/or combine spicy Korean chili flakes along with regular Korean chili flakes. I provided more information about these in the main post above.
If you are not sure whether you can finish the oil soon enough, I recommend you halve the recipe initially.